Low-profile, pivotable heart valve sewing ring

ABSTRACT

A sewing ring for prosthetic heart valves that is connected and configured to pivot outward. A biocompatible fabric covering surrounds at least a portion of the sewing ring, and the ring may be exclusively connected to a stent with the fabric. The sewing ring may be generally planar and of uniform thickness, or may be of varying thickness. The fabric may be used to encompass both the stent and the sewing ring, and may be a single piece. A seam may be provided in the fabric as a discrete pivoting line. The sewing ring may be convertible between bi-stable positions. The ring may extend outward in a frusto-conical shape so as to enable inversion between a position facing the inflow end of the valve and a position facing the outflow end of the valve. The sewing ring may have a compliant insert having a celled construction defined by outer walls and inner ribs. A method of implantation, and a method of assembly of the heart valve is also provided.

RELATED APPLICATIONS

The present application is a continuation of Ser. No. 09/585,098, filedon Jun. 1, 2000 now abandoned, entitled LOW PROFILE HEART VALVE SEWINGRINGS.

FIELD OF THE INVENTION

The present invention relates generally to medical devices andparticularly to heart valve prostheses having a low-profile sewing ringthat enables larger valve orifices to be used.

BACKGROUND OF THE INVENTION

Prosthetic heart valves are used to replace damaged or diseased heartvalves. In vertebrate animals, the heart is a hollow muscular organhaving four pumping chambers: the left and right atria and the left andright ventricles, each provided with its own one-way valve. The naturalheart valves are identified as the aortic, mitral (or bicuspid),tricuspid and pulmonary valves. Prosthetic heart valves can be used toreplace any of these naturally occurring valves, although repair orreplacement of the aortic or mitral valves is most common because theyreside in the left side of the heart where pressures are the greatest.

Two primary types of heart valve replacements or prostheses are known.One is a mechanical-type heart valve that uses a ball and cagearrangement or a pivoting mechanical closure to provide unidirectionalblood flow. The other is a tissue-type or “bioprosthetic” valve which isconstructed with natural-tissue valve leaflets which function much likea natural human heart valve's, imitating the natural action of theflexible heart valve leaflets which seal against each other to ensurethe one-way blood flow. In both types of prosthetic valves, abiocompatible fabric-covered suture or sewing ring or cuff on the valvebody (mechanical) or stent (tissue-type) provides a platform forattaching the valve to the annulus of the particular valve beingreplaced.

The valves of the heart separate chambers therein, and are each mountedin an annulus therebetween. The annuluses comprise dense fibrous ringsattached either directly or indirectly to the atrial and ventricularmuscle fibers. In a valve replacement operation, the damaged leafletsare excised and the annulus sculpted to receive a replacement valve.Ideally the annulus presents relatively healthy tissue that can beformed by the surgeon into a uniform ledge projecting into the orificeleft by the removed valve. The time and spacial constraints imposed bysurgery, however, often dictate that the shape of the resulting annulusis less than perfect for attachment of a sewing ring. Moreover, theannulus may be calcified as well as the leaflets and complete annulardebridement, or removal of the hardened tissue, results in a largerorifice and less defined annulus ledge to which to attach the sewingring. In short, the contours of the resulting annulus vary widely afterthe natural valve has been excised.

Conventional placement of the valve is intra-annular, with the valvebody deep within the narrowest portion of the annulus to enhance anyseal effected by the sewing ring/suture combination and reduce thechance of perivalvular leakage. Surgeons report using at least 30 simplesutures or 20 mattress-type sutures to prevent leakage. Mattress suturesare more time consuming and essentially comprise double passes of theneedle through the tissue with one knot.

Naturally, the implantation of a prosthetic heart valve, either amechanical valve or a bioprosthetic valve (i.e., “tissue” valve),requires a great deal of skill and concentration given the delicatenature of the native heart tissue, the spatial constraints of thesurgical field and the criticality of achieving a secure and reliableimplantation. It is of equal importance that the valve itself hascharacteristics that promote a long valve life and that have minimalimpact on the physiological makeup of the heart environment.

In view of the foregoing, it is evident that an improved sewing ringthat addresses the apparent deficiencies in existing sewing rings isnecessary and desired. That is, there is a need for a sewing ring thatincreases the orifice area of the valve while at the same timesimplifying the fabrication and implantation steps.

SUMMARY OF THE INVENTION

The present invention provides an improved sewing ring and sewingring/stent assembly that facilitates manufacture and implantation ofheart valves. The sewing ring is adapted to pivot or move outward fromthe stent, thus enabling a surgeon during the implantation procedure tomore easily isolate the sewing ring against the native tissue and awayfrom the stent and tissue leaflets. Thus, there is less chance of thesurgeon puncturing the leaflets. Furthermore, the compliance of thesewing ring, or ability to pivot the ring away from the stent, enablesthe sewing ring to be made smaller in the radial dimension, and thus theoverall valve orifice size can be increased. Additionally, themanufacturing process is facilitated because various regions around thestent can be more easily visualized and accessed by virtue of themovable sewing ring.

In one aspect, the present invention provides a sewing ring attached toa generally annular periphery of a heart valve. The sewing ring includesa suture-permeable ring attached to the heart valve periphery andconfigured to pivot from a first position substantially adjacent theperiphery to a second position outward from the first position. Thesewing ring desirably comprises a suture-permeable insert ring and afabric cover. The insert ring may be substantially planar. The fabriccovering the insert ring also desirably covers a portion of the heartvalve. Moreover, the fabric covering both the insert ring and a portionof heart valve also preferably connects the ring to the heart valveperiphery. A seam may be provided wherein the sewing ring pivots betweenthe first and second positions about the seam. In one embodiment, thefirst and second positions are stable such that the sewing ring isbi-stable.

In a further aspect, a heart valve having an inflow end and an outflowend is provided, comprising a generally annular stent, and asuture-permeable sewing ring attached to a periphery thereof. The sewingring is movable between two positions, wherein in the first position thesewing ring extends generally toward the outflow end of the valve and inthe second position the sewing ring extends generally toward the inflowend of the valve. The sewing ring may comprise an insert ring and afabric cover, and the fabric covering the insert ring may also cover aportion of the stent. In a preferred embodiment, the sewing ringattaches to the stent exclusively with a portion of a fabric that alsocovers a portion of the sewing ring. A seam is desirably provided in thefabric at the line of attachment between the sewing ring and the stent,wherein the sewing ring pivots about the seam between the first andsecond positions. The first and second positions may be stable, and theinsert ring may be frustoconical in shape such that in the firstposition the ring extends toward the outflow end and in the secondposition the ring extends toward the inflow end. Furthermore, the insertring may be provided with alternating radially thick and thin regions,or it may have a radially unulating shape, to facilitate movementbetween the first and second positions.

In another aspect, the present invention provides a heart valveincluding a generally annular stent having a periphery, a tubularfabric, and a generally annular suture-permeable insert sized at leastas large as the stent periphery. The stent and insert are connectedtogether exclusively by a portion of the fabric that permits relativeoutward pivoting of the insert with respect to the stent. In a preferredembodiment, the fabric at least partly covers both the stent and insert.A seam may be provided in the fabric at the line of attachment betweenthe insert and the stent to provide a discrete pivot line. In apreferred embodiment, the tubular fabric is a single piece prior toassembly of heart valve, and desirably encompasses both the stent andinsert. The stent may have an undulating outflow edge comprisingalternating commissures and cusps, wherein the fabric covers the outflowedge. The insert is desirably disposed around stent to pivot about theouter surface thereof, and a sewing tab along the undulating outflowedge is desirably sewn directly to the stent to prevent relativemovement of the fabric upon pivoting of the insert.

In a further embodiment, a method of implanting a heart valve in hosttissue (e.g., an aortic annulus) is provided. The heart valve has aninflow end and an outflow end, and a sewing ring attached to a peripherythereof. The method includes positioning the sewing ring to extendgenerally toward the inflow end of the valve, attaching the sewing ringto the host tissue, and re-positioning the valve with respect to theattached sewing ring so that the sewing ring extends generally towardthe outflow end of the valve. The method of attachment preferablycomprises suturing. The method also may include providing the heartvalve having a stent and a plurality of leaflets supported thereby, thesewing ring being located substantially adjacent the valve whenextending generally toward the inflow end of the valve. The method ofre-positioning may thus include inverting the sewing ring by pivoting itoutward from the position substantially adjacent the valve. In oneembodiment, the sewing ring is configured and attached to the stent soas to be bi-stable between the two positions.

Further, the present invention provides a method of assembling a heartvalve, including providing a generally annular stent having a periphery,a tubular fabric, and a generally annular suture-permeable insert ringsized at least as large as the stent periphery. The method includesconnecting the stent and insert ring with the fabric to permit relativeoutward pivoting of the fabric-covered insert ring with respect to thestent. The method may include completely covering the stent with thetubular fabric prior to connecting the insert ring with the fabric.Furthermore, the tubular fabric preferably consists of a single piece,wherein the method includes covering both the stent and the insert ringwith the single piece. The method further may include holding a portionof tubular fabric against the annular stent using an assembly fixture.The assembly fixture desirably comprises an annular member and ismounted for rotation about an assembly handle. The handle has anelongated grip, wherein the axis of rotation of the assembly fixture isangled with respect to the grip.

A further understanding of the nature and advantages of the inventionwill become apparent by reference to the remaining portions of thespecification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a stent assembly used in an exemplarymitral or pulmonary position heart valve of the present invention;

FIG. 2 is a perspective view of a suture-permeable insert for anexemplary mitral or pulmonary position heart valve sewing ring of thepresent invention;

FIGS. 3A and 3B are perspective views of initial steps in an assemblyprocess of a heart valve of the present invention wherein a tubularfabric covering is wrapped around the stent assembly of FIG. 1;

FIG. 3C is a cross-sectional view taken along line 3C-3C of FIG. 3B;

FIGS. 4A and 4B are perspective views of further steps in the heartvalve assembly process in which the fabric covering is attached alongthe outflow edge of the stent assembly;

FIG. 5A is a perspective view of a further step in the heart valveassembly process in which free edges of the tubular fabric covering arecreated in preparation for addition of the insert shown in FIG. 2;

FIG. 5B is a cross-sectional view taken along line 5B-5B of FIG. 5A;

FIG. 6A is a perspective view of a further step in the heart valveassembly process wherein the insert of FIG. 2 is positioned around thestent assembly of FIG. 1, with the fabric covering therebetween, andwith the help of an assembly fixture;

FIG. 6B is a cross-sectional view taken along line 6B-6B of FIG. 6A;

FIG. 7A is a perspective view of a further step in a heart valveassembly process wherein an outflow portion of the suture-permeableinsert is covered with the help of a suturing fixture;

FIG. 7B is a cross-sectional view taken along line 7B-7B of FIG. 7A;

FIG. 8A is a perspective view of a subassembly of the heart valve of thepresent invention including the fabric-covered stent assembly and sewingring;

FIG. 8B is a cross-sectional view taken along line 8B-8B of FIG. 8A;

FIG. 9A is a perspective view of the subassembly of FIG. 8A mounted on afinal assembly handle of the present invention;

FIG. 9B is a partial sectional view of the subassembly taken along line9B-9B of FIG. 9A and mounted on the final assembly handle;

FIG. 10 is a partial sectional view of a step in the final assemblyprocess wherein the sewing ring of the present invention pivots awayfrom the stent assembly to facilitate suturing tissue valve leaflets anda wireform subassembly thereto;

FIGS. 11A-11C are elevational views of a stent/sewing ring subassemblyof an exemplary aortic or pulmonic heart valve of the present inventionillustrating conversion of the sewing ring between two bi-stablepositions;

FIGS. 12A-12D are various views of a suture-permeable insert for thesewing ring of the subassembly of the exemplary heart valve seen inFIGS. 11A-11C;

FIGS. 13A and 13B are cross-sectional views through the stent/sewingring subassembly of FIGS. 11A-11C illustrating in more detail the sewingring in the bi-stable positions;

FIG. 14 is an elevational view of a stent/sewing ring subassembly of afurther exemplary aortic or pulmonic heart valve of the presentinvention in a valve implant position of the sewing ring;

FIGS. 15A-15C are various views of a suture-permeable insert for thesewing ring of the subassembly seen in FIG. 14;

FIGS. 16A and 16B are an elevational view and cross-section,respectively, of a valve having the stent/sewing ring subassembly ofFIG. 14 during an attachment step of implantation; and

FIGS. 17A and 17B are an elevational view and cross-section,respectively, of a valve having the stent/sewing ring subassembly ofFIG. 14 during a seating step of implantation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an improved heart valve sewing ring thatenables an increase in the effective orifice size of the valve withoutincreasing the overall valve outer diameter. Sewing rings for a mitralheart valve and an aortic heart valve are illustrated herein, but thoseof skill in the art will understand that many of the inventive conceptsare applicable to heart valves for the pulmonary or tricuspid valvepositions. More specifically, the annulus for the mitral and tricuspidpositions are generally planar and non-scalloped, while the annulus forthe aortic and pulmonary positions are generally scalloped or undulating(i.e., three dimensional). Therefore, certain sewing ring featuresdisclosed herein may be more or less suitable to a planar or scallopedannulus. Moreover, although certain features are described asparticularly suited to either the mitral (planar annulus) or aortic(scalloped annulus) valve designs, such features in other constructionsmay be applicable to both valve designs. Finally, although variousmaterials and dimensions maybe described as preferred herein, othermaterials and dimensions may work equally well and are not necessarilyexcluded.

The present invention also describes various steps in the assemblyprocess of heart valves to form the sewing rings of the presentinvention. It should be understood that the assembly steps may beaccomplished in a different order, and an assembly process in accordancewith the present invention may not include all of the steps describedand illustrated herein. Furthermore, additional steps in the assemblyprocess may be included other than those specifically disclosed.

FIGS. 1 and 2 illustrate two components of a tissue-type heart valve ofthe present invention for use in a non-scalloped annulus (i.e., mitralor tricuspid). Specifically, FIG. 1 illustrates a stent assembly 20comprising an annular, flexible, inner member 22, and an annular, outermember 24 that is relatively less flexible than the inner member. Boththe inner member 22 and the outer member 24 are desirably formed asthin-walled bands that contact one another at their facing surfaces. Theinner member 22 includes an outflow edge 26 that alternates betweencurvilinear cusps 28 and upstanding commissures 30.

The stent assembly 20 is used in the construction of a tri-leaflet heartvalve, wherein three bio-prosthetic leaflets are suspended within thevalve orifice and are attached around the valve generally along theoutflow edge 26 of the inner member 22. In other valves that could beconstructed in accordance with present invention, more or less thanthree leaflets may be utilized, with the number of cusps 28 andcommissures 30 varying accordingly.

The outer member 24 also includes an outflow edge that includescurvilinear cusps 32 juxtaposed with the cusps 28 of the inner member22. Instead of continuing upward at the commissures, however, the outermember 24 terminates at straight edges 34 rendering the commissures 30of the inner member 22 unsupported, and therefore highly flexible. In apreferred embodiment, the inner member 22 is formed of a polymer,preferably MYLAR, while the outer member 24 is relatively more rigid,and may be a biocompatible metal such as ELGILOY.

The inner member 22 is secured to the outer member 24 via a plurality ofthrough holes 36 and attachments sutures 38. In other embodiments, thestent assembly 20 maybe formed of a single member, or the members 22, 24may be fastened together using adhesive or other suitable means.

FIG. 2 illustrates an exemplary suture-permeable sewing ring insert 40used in the construction of the mitral heart valve of the presentinvention. The insert 40 is generally annular and includes a solid,preferably curvilinear inflow surface 42, a solid, generally tubularinner wall 44, and an open-celled outflow face 46. The insert 40 may bemolded of a biocompatible material such as silicone rubber, and includesa plurality of internal ribs 48 defining voids 50 therebetween to makeup the open-celled construction. An outer edge 52 of the outflow face 46is desirably circular, and in one plane, while the inner edge 54 (formedby the outflow edge of the inner wall 44) includes a series ofdepressions 56; specifically three, in accordance with the tri-leafletdesign of the illustrated heart valve. The depressions 56 receive cuspportions of a wireform of a heart valve and help prevent axial movementof the wireform and leaflets with respect to the sewing ring. Suchconstruction is shown and described in U.S. Pat. No. 5,928,281, issuedJul. 27, 1999, which disclosure is hereby expressly incorporated byreference. Because the valve position for which the sewing ring insert40 is useful is non-scalloped, the insert 40 is substantially planar.Furthermore, the exemplary insert 40 is of uniform thickness about itscircumference, although non-uniform configurations are possible.

FIGS. 3A-3C illustrate initial steps in an assembly process for themitral heart valve of present invention in which a tubular fabriccovering 60 is draped over the stent assembly 20. The fabric covering 60may be a variety of materials, but is typically a polyester such aspolyethylene terepthalate. In FIG. 3A, the tubular fabric covering 60 isshown around the outside of the stent assembly 20 with an upper edge 62folded down and in so as to be radially inside the upper ends of thecommissures 30. A fold line 64 is disposed a distance A above the tipsof the commissures 30, which distance is desirably about 1 mm. Aplurality of pins 66 or other such temporary fixation devices areutilized to maintain the relative position of the fabric covering 60 inthis folded configuration.

FIGS. 3B and 3C show a subsequent step in the attachment of the stentassembly 20 and the fabric covering 60 wherein the lower edge 68 seen inFIG. 3A has been folded inward and pulled upward through the middle ofthe stent assembly to be disposed above the fold line 64. The lower edgeof the fabric covering 60 is thus defined by a second fold line 70disposed some distance below the stent assembly 20. Again, a pluralityof pins 72 may be used to temporarily hold the relative positions of thestent assembly 20 and fabric covering 60.

At this stage, as seen in FIGS. 4A and 4B, a backstitch seam 74 is addedbelow the stent assembly 20 to join the inner and outer tubular portionsof fabric covering 60. The backstitch seam 74 is more clearly shown inthe cross-section of FIG. 5B. FIGS. 4A and 4B schematically illustrate aconventional process of trimming and sewing the upper portions of thefabric covering 60 so as to form a rolled fabric sewing tab 76 along theupper edge of the stent assembly 20. Specifically, the sewing tab 76extends generally outward from the stent assembly 20 and comprisesseveral layers of the fabric covering 60 rolled together and sutured inplace, such as with stitches 78 seen in FIGS. 4A and 4B. Details of theprocess of forming the sewing tab 76 will be omitted for brevity, butthose of skill in the art will understand that there are various ways toform such a tab.

At this stage, and as seen in FIGS. 5A and 5B, the lower length of thefabric covering 60 below the backstitch seam 74 will be severed at thefold line 70 (FIG. 3C) to form a first, outer tubular portion 82, and asecond, inner tubular portion 84. As will be described, the tubularportions 82, 84 ultimately wrap around the ring-shaped insert 40 to forma sewing ring of the heart valve. In this regard, the outer tubularportion 82 is first inverted from its downward position around the innertubular portion 84 into the upwardly-extending position shown in FIG. 5Asurrounding the fabric-covered stent 80. Additionally, the backstitchseam 74 defines a circular line about which the sewing ring will pivot.

With reference to FIGS. 6A-6B, the aforementioned ring-shaped insert 40is shown positioned around the fabric-covered stent 80, with the uppertubular fabric portion 82 interposed therebetween. As mentionedpreviously, the ring-shaped insert 40 includes a plurality of internalribs 48, some of which extend radially. The cross-section shown in FIG.6B is taken through one of these radial ribs 48 and illustrates aportion of the axially-extending inner wall 44 disposed substantiallyadjacent and parallel to the outer member 24 of the stent assembly 20(with reference back to FIG. 1). The inner member 22 of the stent 24 isalso shown juxtaposed against the outer member 24. The insert 40therefore extends generally radially outward from the stent assembly 20,with two layers of the fabric covering 60 disposed therebetween. Itshould be noted that said two layers of fabric covering (one of which isa portion of the fabric covering encompassing the stent assembly 20, andone of which is the upper tubular portion 82) are not connected in theaxial space between the stent assembly 20 and insert 40. Instead, thetwo layers of fabric covering extend underneath the stent assembly 20and are joined together at the backstitch seam 74.

FIGS. 6A and 6B also illustrates an annular assembly fixture 90 having atubular axial wall 92, and a radial flange 94 extending outwardtherefrom. The wall 92 is sized to fit closely adjacent the inner wallof the fabric-covered stent 80, while the flange 94 is positioned justbelow both the stent assembly 20 and insert 40, with one or more layersof the fabric covering 60 disposed therebetween. The fixture 90 causesthe inner tubular portion 84 of the fabric covering 60 to bend outwardat the backstitch seam 74 and presses it against the underside of thegenerally aligned stent assembly 20 and insert 40. Indeed, thecombination of the sewing tab 76 and the fixture 90 axially positionsthe insert 40 with respect to the stent assembly 20. During assembly,the ring-shaped insert 40 is pushed upward against the sewing tab 76,and then the fixture 90 added to hold the insert in this preferredposition. The combined length of the inner tubular portion 82 and outertubular portion 84 of the fabric covering 60 is sufficient to encompassthe insert 40, as will be explained below.

Now with reference to FIGS. 7A and 7B, a further step of adding a flat,suture-permeable ring 100 to the assembly of the heart valve is shown.First, the inner tubular portion 82 is folded outward to cover theoutflow face 46 (FIG. 2) of the insert 40 and severed to form an edge102 at the circular outer edge 52 of the insert. The suture-permeablering 100 is then positioned on top of the tubular member 82, and asewing fixture 104 is utilized to press the elements flat. Thesuture-permeable ring 100 stiffens the insert 40. That is, in apreferred embodiment, the insert 40 is silicone rubber, and the ring 100is a stiff textile, preferably non-woven polyester. One particularlypreferred material is sold under the trade name REMAY manufactured byRemay, Inc., Old Hickory, Tenn.

FIG. 7A illustrates the sewing fixture 104 in perspective, showing aplurality of apertures 106 that receive the commissure portions of thefabric-covered stent 80 projecting therethrough. The apertures 106 serveto center the annular sewing fixture 104 with respect to thefabric-covered stent 80 and insert 40. As seen in FIG. 7B, the sewingfixture 104 includes an inner axially extending wall 108 that fits justinside the axial wall 92 of the assembly fixture 90, and a radial flange110 extending outward therefrom. The radial flange 110 has a taperedouter edge 112 that terminates short of the outer edge of thesuture-permeable ring 100. As illustrated, the ring 100 is size suchthat its outer edge is aligned with the insert edge 52 and the edge 102of the tubular portion 82. Consequently, a stitch 114 is passed aroundthe circumference of the insert 40, joining the insert to both thetubular portion 82 and suture-permeable ring 100 at their respectiveouter edges. The sewing fixture 104 facilitates the stitching operationbecause the tapered outer edge 112 provides a clear circular guide. Thatis, the sewing fixture 110 maintains the respective elements sandwichedtogether (in conjunction with the assembly fixture 90), and exposes justa small peripheral portion of the ring 100 through which the fabricatorpasses the sewing needle. After this operation, the sewing fixture 104is removed.

FIG. 7B also illustrates the arrangement of the fabric covering 60around both the stent assembly 20 and the insert 40 at the commissureregions. In particular, the initial single piece of fabric is shownentirely encompassing the stent assembly 20, and partially encompassingthe insert 40.

FIGS. 8A and 8B illustrate a completed stent/sewing ring subassembly 120comprising the cloth-covered stent 80 attached to the cloth-coveredinsert 40, or sewing ring 122. The inner tubular portion 84 of the clothcovering has been wrapped upward and inward around an inner edge 124 ofthe suture-permeable ring 100. The terminal end of the tubular portion84 is folded or otherwise disposed within a recess formed by therecessed ribs 48 of the insert 40. To complete the sewing ring 122, acircular line of stitches 126 is provided through the tubular portion84, inner edge of the ring 100, insert 40, and outer tubular portion 82.Again, the sewing ring 122 is exclusively attached to the fabric-coveredstent 80 using the cloth covering 60, and specifically, the twocomponents pivot with respect to one another about the backstitch seam74. It should be noted that although the subassembly 120 is complete,the assembly fixture 90 remains in position for subsequent assemblysteps.

Prior to attaching a wireform and tissue leaflets to the stent/sewingring subassembly 120, an assembly handle 130 is introduced, as seen inFIGS. 9A and 9B. The handle 130 comprises a generally elongated grip 132and a valve seat 134 rotatable dispose about one end. The valve seat 134is mounted to rotate about an axis 136 that is angled with respect tothe longitudinal axis of the elongated grip 132. The valve seat 134 hasa stepped configuration with a base flange 138 and an upstandingcylinder 140. The stepped configuration of the valve seat 134 is sizedto fit closely against the assembly fixture 90, as seen in FIG. 9B. As aresult, the stent/sewing ring subassembly 120 can be rotatably mountedabout one end of the handle 130 at an angle with respect to the grip132.

FIG. 10 illustrates a further assembly step wherein a wireformsubassembly 140 and a plurality of leaflets 142 are attached to thestent/sewing ring subassembly 120. Specifically, a fabricator grips thehandle 130 and is able to pivot the sewing ring 122 radially outwardfrom the fabric-covered stent 80, as seen by arrow 144, to facilitatemanipulation of a needle 146 having thread 148 attached thereto. Theneedle 146 is used to form a stitch line (not shown) joining thewireform subassembly 140 to the fabric-covered stent 80, andspecifically to the rolled fabric tab 76. Outer edges of the leaflets142 are positioned between the stent 80 and wireform subassembly 140such that the stitch line also passes therethrough. The flexibleleaflets together provide the occluding surfaces of the valve.

Because of the ability to rotate the stent/sewing ring subassembly 120about the angled handle 130, the same operation of pivoting the sewingring 122 outward to facilitate formation of the stitch line can easilybe performed around entire periphery of the heart valve. The outwardpivoting of the sewing ring 122 results in greater visibility of thearea in which the stitch line is formed, and reduces the chance ofinadvertent puncture of components of the heart valve other than thoseintended.

FIGS. 11A-11C illustrates an alternative stent/sewing ring subassembly150 of the present invention in which a sewing ring 152 extends outwardfrom a stent 154 and can be inverted from a position generally facingthe inflow end of the subassembly (FIG. 11C), to a position generallyfacing the outflow end (FIG. 11A). As with the earlier describedembodiment, the stent/sewing ring subassembly 150 includes a fabriccovering that is desirably formed from a single piece of tubular fabric,as will be explained below. The stent 154 includes a plurality ofupstanding commissure posts 156 extending toward the outflow endseparated by cusp regions 158 that are convexly curved toward the inflowend. Although not shown in FIGS. 11A-11C, the stent 154 in conjunctionwith a wireform provides support for a plurality of flexible leafletstherebetween. The flexible leaflets together provide the occludingsurfaces of the valve, and in a preferred embodiment are formed frombovine pericardial tissue.

Although the stent/sewing ring subassembly 150 can be used in a varietyof positions within the heart, it is particularly useful in the aorticposition which has a scalloped, three-dimensional configuration. Theaortic valve is located at the outflow of the left ventricle, betweenthe ventricle and the ascending aorta. Prosthetic aortic valves aretypically sutured (or attached by other means) to the annulus tissueremaining after the defective host valve has been excised. The annulustissue forms a tough, fibrous ledge extending inward from thesurrounding anatomy to define a generally circular orifice between theventricle and the ascending aorta. An exemplary implantation positionfor an aortic valve is illustrated in FIG. 11A, with a host annulus 160indicated in dashed line. The stent/sewing ring subassembly 150 is alsosuitable for implant in the pulmonary position, which has a scallopedconfiguration, although such valve replacement procedures are lesscommon.

A typical method of implantation includes passing a plurality of suturesthrough the prepared annulus prior to valve delivery. The suture lengthsextend out of the surgical field and body and can thus be easily passedthrough the corresponding locations on the sewing ring, thus “attaching”the valve to the annulus. Subsequently, the valve is gently loweredalong the array of sutures into position in contact with the annulus,and multiple knots formed securing each pair of suture lengths to thesewing ring. The ability to invert the sewing ring 152 into the positionshown in FIG. 11C, generally extending toward the inflow end of thevalve, provides a degree of separation of the sewing ring from the stent154, and leaflets support thereby. As a result, the valve including theinverted sewing ring 152 as in FIG. 11C can be “attached” to the hostannulus with a reduced risk of puncturing the fragile tissue leaflets.That is, the task of passing the sutures through the sewing ring issimplified because the sewing ring can be pivoted to extend away fromthe valve body and leaflets. Before or after contact with the annulus160, the sewing ring 152 can be inverted as in FIG. 11B into theimplantation position of FIG. 11A. Because the greatest axial forces onthe aortic valve are during diastole from pressure built up on theoutflow side of the valve, the valve will be forced against the annulus160 and the sewing ring 152 will remain in the position of FIG. 11A.

FIGS. 12A-12D and 13A-13B illustrate various details of the stent/sewingring assembly 150, and in particular the attachment configurationbetween the sewing ring 152 and stent 154. FIGS. 12A-12D are variousviews of a ring-shaped insert 160 that, in conjunction with a fabriccovering 162 (FIGS. 13A-13B), defines the sewing ring 152.

As seen in the plan view of FIG. 12A, the insert 160 includes a circularouter edge 164 and an inner edge 166 having alternating regions ofincreased (168) and decreased (170) radial thickness, corresponding tothe cusps and commissure regions, respectively, of the sewing ring 152formed thereby. With reference to the cross-sectional views of FIGS. 12Band 12C, the insert 160 is primarily defined by a band that is angledoutward to form a frustoconical shape. The outward angle θ of the band172 is preferably in the range of about 20° and 45°, and more preferablyis about 30°. The band 172 extends around the entire periphery of theinsert 160, and a plurality of circular ribs 174 are provided on theouter face thereof. FIG. 12C illustrates the regions 168 of increasedthickness, which are formed in the cusps of the sewing ring 152 by acurvilinear lower portion 176 and a plurality of upstanding walls 178.The regions of increased (168) and decreased (170) radial thickness helpthe sewing ring 152 invert from an orientation extending generallytoward the outflow end of the valve and an orientation extendinggenerally toward the inflow end. The walls 178 are seen in the plan viewof FIG. 12A and define a celled structure. In a preferred embodiment,the insert 160 is molded from silicone rubber.

The insert 160 is shown in two configurations herein; a firstconfiguration being shown in FIGS. 12C and 12D with an internalstiffening member 180 embedded within the band 172, and also within thethickened regions 168. In the second configuration, seen in FIGS. 13Aand 13B, a stiffening member 182 that is separate from the insert 160 isprovided, attached to the insert using the fabric covering 162. Both theembedded stiffening member 180 and the separate stiffening member 182serve the same purpose, that is stiffening the relatively soft andflexible insert 160. The stiffening members 180 or 182 are relativelymore stiff than the material of the insert 160, and may be made from anon-woven polyester.

The other main components of the heart valve constructed using thestent/sewing ring subassembly 150 are illustrated in cross-section inFIGS. 13A and 13B. The valve includes a stent assembly 190 formed by acombination of an inner stent member 192 and an outer stent member 194,much like the members 22 and 24 illustrated in FIG. 1. The stentassembly 190 is encompassed by a fabric cover, preferably an extensionof the fabric cover 162 around the sewing ring 152. A plurality oftissue leaflets 196 is secured to the outflow end of the stent 154 usinga wireform subassembly 198. The overall shape of the heart valve issimilar to the embodiment described earlier, as is evident from FIGS.11A-11C.

As with the earlier embodiment, the fabric cover 162 is desirably formedfrom a single piece of tubular fabric. The assembly steps are similar tothose described above for the first embodiment, and include wrapping thetubular fabric around the stent assembly 190 so that the free endsthereof can be joined together in a rolled sewing tab 200. In contrastto the earlier embodiment, the stent assembly 190 is provided with aplurality of through holes 202 extending in a line proximate the outflowedge thereof to enable passage of a stitch line 204 attaching the sewingtab 200 to the stent assembly. In particular, both the inner member 192and outer member 194 include a plurality of through holes that arealigned for this purpose. The utility of this added stitch line 204 willbecome apparent below.

As with the first embodiment, the tubular fabric is severed to definetwo tubular portions that wrap around the insert 160 (and separatestiffening member 182 if provided) to form the sewing ring 152. Inparticular, an inner tubular portion 210 extends around the inflow sideof the insert 160 and an outer tubular portion 212 extends around theoutflow side. The outer tubular portion 212 covers the outflow face ofthe insert 160 and is severed at 214 at the circular outer edge 164. Ifa separate stiffening member 182 is used, as illustrated FIGS. 13A and13B, a stitch line 216 secures it to the outer edges of the insert 160and outer tubular portion 212. Otherwise, the stitch line 216 justsecures the outer tubular portion 212 to the insert 160. The innertubular portion 210 extends around the outer edge 164 and is secured toboth the outer tubular portion 212 and insert 160 somewhere on theoutflow face of the sewing ring. In the illustrated embodiment, where aseparate stiffening member 182 is used, the inner tubular portion 210wraps around the stiffening member and a free end 218 is trapped betweenthe stiffening member and the outer tubular portion 212 and secured inthat position using a line of stitches 220.

The sewing ring 152 pivots outward from the position generally adjacentthe stent 154 shown in FIG. 13A to the position shown in FIG. 13B. Theposition shown in FIG. 13A corresponds to FIG. 11A, wherein the sewingring 152 extends generally toward the outflow end of the valve, whilethe position shown in FIG. 13B corresponds to that shown in FIG. 11C,with the sewing ring extending generally toward the inflow end.

The only connection between the sewing ring 152 and the stent 154 isprovided by the fabric cover 162 (i.e., there are no stitch linesbetween the insert 160 and the stent assembly 190, or fabric coveringsthereon). The portions of the fabric covering 162 around the sewing ring152 and stent 154 are distinguished at a seam 222, which provides adiscrete pivot line (a point in cross-section) for the sewing ring. Theseam 222 is located on the exterior of the stent 154, as opposed tobeing located on the inflow end of the stent, as was the case with theearlier described embodiment (see, e.g., FIG. 8B). Therefore, the sewingring 152 pivots about the periphery of the stent 154.

The utility of the stitch line 204 connecting the rolled sewing tab 200to stent assembly 190 will now be apparent. As the sewing ring 152pivots between the position shown in FIG. 13A to the position shown inFIG. 13B, tension will be applied to the fabric cover 162 that tends torotate the cover around the stent assembly 190 in a clockwise direction,from the perspective of the drawings. The stitch line 204 maintains theposition of the rolled sewing tab 200 at the outflow end of the stent154, and resists this tendency to rotate about the stent assembly 190.

Because of the novel connection between the sewing ring 152 and stent154, the two positions shown in FIGS. 11A/13A and 11C/13B are bi-stable.Specifically, the band 172 of the insert 160 creates a generallyfrustoconical sewing ring 152 that can be inverted between orientationsextending toward the outflow end and the inflow end. The resiliency ofthe insert 160 means that the outer circular edge 164 is stretched andplaced in tension as it passes between the two positions, thus biasingthe insert one way or the other. This bi-stable configuration greatlyassists during both the manufacturing process, and the implantationprocedure, as mentioned above. During manufacture, the fabric-coveredstent/sewing ring subassembly 150 is constructed, and the tissueleaflets 196 and wireform assembly 198 are added. Because the sewingring 152 can be pivoted away from the stent 154, attaching the leaflets196 and wireform assembly 198 is simplified. That is, the suturingneedle can more easily be passed through the various components to formthe stitch line 230 when the sewing ring 154 is displaced out of theway. Various fixtures may be used during the assembly process as wasdescribed above with respect to the first embodiment.

As mentioned above, the particular shape of the insert 160 furtherfacilitates inversion of the sewing ring 152 between the two stablepositions. With reference back to FIG. 12A, the alternating radiallythick (168) and thin (170) regions provide areas of varying bendingstrength in the insert 160. As a result, the cusp regions of thefrustoconical band 172 can more easily be pivoted outward because of thethin regions 170 at the commissures, which present relatively littleresistance to bending. Conversely, because of the thick regions 168, theinsert 160 tends to snap between the two stable positions. That is, thethick regions 168 provide some rigidity to the structure.

FIG. 14 illustrates a further exemplary stent/sewing ring subassembly250 of the present invention in which a sewing ring 252 extends outwardfrom a stent 254 and can be inverted from a position generally facingthe inflow end of the subassembly, to the illustrated position shown,generally facing the outflow end. As with the earlier describedembodiment, the stent/sewing ring subassembly 250 includes a fabriccovering that is desirably formed from a single piece of tubular fabric.The stent 254 includes a plurality of upstanding commissure posts 256extending toward the outflow end separated by cusp regions 258 that areconvexly curved toward the inflow end. Although not shown in FIG. 14,the stent 254 in conjunction with a wireform provides support for aplurality of flexible leaflets therebetween. The flexible leafletstogether provide the occluding surfaces of the valve. In a preferredembodiment, the flexible leaflets are formed from bovine pericardialtissue.

The stent/sewing ring subassembly 250 is in many ways similar to thesubassembly 150 in FIGS. 11-13, but has a reduced size sewing ringinsert 260 that provides distinct advantages. With reference to FIGS.15A-15C, as seen prior to assembly in the subassembly 250, the insert260 includes an undulating outer edge 264 and an undulating inner edge266. With reference to the cross-sectional view of FIG. 15C takenthrough a commissure region, the insert 260 is defined by a band 270that is angled outward to form a frustoconical shape and a plurality ofoutwardly extending ribs 272. There are no celled walls as in theprevious embodiment, except for vestiges described below, and the radialdimension has been decreased from the version seen in FIGS. 12A-12C.Again, the outward angle of the band 270 is preferably in the range ofabout 20° and 45°, and more preferably is about 30°. The band 270extends in a continuous fashion around entire periphery of the insert260. An internal stiffening member 274 may optionally be embedded withinthe band 270. In a preferred embodiment, the insert 260 is molded fromsilicone rubber.

The outer edge 264 and inner edge 266 undulate in juxtaposition to formthree commissure regions 276 extending radially outward from andseparated by three cusp regions 278. The radial dimension of theexemplary insert 260 is generally constant around its circumference,although small reinforcing ribs 279 may be provided on the insidesurface of the cusp regions 278 for stability during manipulationbetween inflow and outflow orientations. As with the earlier embodimentwith varying thickness, the undulating shape of the insert 260 helpsfacilitate the pivoting inversion, and also helps the sewing ring 252formed thereby conform to the scalloped (undulating) shape as seen inFIG. 14.

The insert 260 is seen in cross-section in FIGS. 16B and 17B assembledinto a valve 280 having the stent/sewing ring subassembly 250. FIG. 16Bshows the sewing ring 252 extending generally toward the inflow end ofthe valve, while FIG. 17B shows the sewing ring 252 extending generallytoward the outflow end of the valve. These two positions are reflectedin the elevational views of FIGS. 16A and 17A, which show two steps in avalve implantation procedure.

Prior to discussing the use, however, the structure of the stent/sewingring subassembly 250 is somewhat modified from that shown in FIGS.11-13. Specifically with reference to FIGS. 13A and 13B, the stent 154is seen extending below the sewing ring on the inflow side of the valve.This arrangement is suitable for intra-annular placement (e.g., where aportion of the valve is within the annulus proper), but not suitable forsupra-annular placement, where no portion of the valve is within theannulus. In contrast to the earlier embodiment, the valve 280 includesthe sewing ring 252 attached at the inflow end of the stent 254 aroundthe entire periphery thereof. As before, the sewing ring 252 attaches tothe stent 254 at a seam line 282 at this inflow end. As a result, thesewing ring 252 pivots about the stent 254 along the seam line 282 (seeFIGS. 16B and 17B).

Although the valve 280 having the stent/sewing ring subassembly 250 canbe used in a variety of positions within the heart, it is particularlyuseful in either the aortic or pulmonic position which have a scalloped,three-dimensional configuration. Two steps in the implantation sequenceillustrating the advantageous use of the sewing ring are shown in FIGS.16A and 17A. Again, the positions of the sewing ring 252 in these twosteps are shown in cross-section of the valve in FIGS. 16B and 17B.

Typically, a plurality of sutures 290 are passed through the annulustissue 292 and extended out of the surgical field (and normally out ofthe patient's body as well). The sutures are grouped in interruptedpairs that will eventually be tied off at the sewing ring. Each pair ofsutures is passed through the sewing ring 252 as shown, with the sewingring in the outward pivoted configuration. In this way, the surgeon hasgreater access to the sewing ring 252 and there is less chance ofpuncturing a leaflet or other delicate valve structure. The valve 280 isseen attached to a conventional holder 294 at the distal end of adelivery handle 296.

Subsequently, as seen in FIG. 17A, the valve is gently guided along thearray of pairs of sutures until the sewing ring 252 seats in contactwith the annulus. In the illustrated embodiment, the sutures arepositioned such that the valve 280 sits in the supra-annular position,not within the annulus proper. Prior to or as the valve 280 meets theannulus tissue 292, the sewing ring 252 pivots or converts back into theposition seen in FIGS. 14 and 17B, generally extending toward theoutflow end of the valve. The pairs of sutures 290 are then tied of atthe sewing ring 252, as seen at 298. Again, backflow forces will simplyforce the valve against the annulus, and will not unduly stress thesutures or cause the sewing ring 252 to revert back to the implantorientation.

In a specific example of the advantages of the stent/sewing ringsubassembly 250, a sewing ring 252 having a modified insert 260 sizedfor use with 21 mm diameter valves can be combined with a 23 mm valve.In other words, the pivoting action of the sewing ring 252 permits asmaller sewing ring to be used with a particular valve size with equaleffectiveness as would be obtained with a conventional, larger sewingring. Moreover, the valve orifice is increased for a lower pressure dropacross the valve, and the small sewing ring 252 helps ensure that thecoronary ostia are not occluded, which is often a worry in thesupra-annular position.

The ability of the sewing rings of the present invention to pivotoutward from the respective stents enables the resulting heart valve tohave a larger orifice in comparison to earlier valves having the sameouter diameter. This is a function of being able to pivot or invert thesewing ring outward during the implantation procedure. Because of thischaracteristic, the surgeon can more easily isolate the sewing ring withrespect to the stent, and there is less likelihood of inadvertentlypuncturing one of the tissue leaflets, for example. The sewing ring canthus be made smaller in its radial dimension in comparison to earliersewing rings, which could not pivot outward away from the stent. Suchearlier sewing rings thus had to be made somewhat larger to give thesurgeon a sufficient suturing platform away from the tissue leaflets.Because the sewing ring of the present invention can be made smaller, alarger valve orifice can be used for the same outer valve diameter.

Moreover, the ability to pivot the sewing rings of the current inventionaway from stent facilitates manufacture, as was clearly illustrated inFIG. 10. That is, the smallest valves have a diameter of about 19 mm,and the reader can appreciate that the sewing process for such a smallvalve is extremely exacting and time-consuming. Indeed, the stitching istypically performed under a magnifying glass. The present inventionreduces the strain associated with such a detailed assembly process. Theability to effectively separate the sewing ring from the stent greatlyincreases the accessibility and visibility of the rolled sewing tab, forinstance.

Finally, the present invention provides an extremely simplifiedconstruction of heart valve. That is, a single piece of tubular fabricis used to encompass both the stent and the sewing ring. The sametubular fabric forms the only connection between two components.Moreover, a minimum number of stitch lines are required, in contrastwith earlier valves. With reference to FIG. 8B, the first embodimentrequires a total of four stitch lines to encompass both the stent andsewing ring. The second embodiment, as seen in FIG. 13A, also requires atotal of four stitch lines, in addition to a desirable fifth stitch line204 to help prevent relative movement of the cloth around the stentassembly 190. In earlier tissue heart valves, additional stitch lineswere required, thus increasing the assembly time and concurrent expense.

While the foregoing is a complete description of the preferredembodiments of the invention, various alternatives, modifications, andequivalents may be used. Moreover, it will be obvious that certain othermodifications may be practiced within the scope of the appended claims.

1. A sewing ring attached to a generally annular periphery of aprosthetic heart valve having an inflow end and an outflow end,comprising: a suture-permeable ring attached to the heart valveperiphery and configured to pivot from a first position extendinggenerally toward the outflow end of the valve to a second positionextending generally toward the inflow end of the valve, wherein firstand second positions are stable such that the sewing ring is bi-stable.2. The sewing ring of claim 1, wherein the sewing ring comprises asuture-permeable insert ring and a fabric cover.
 3. The sewing ring ofclaim 2, wherein the insert ring is substantially planar.
 4. The sewingring of claim 2, wherein the fabric covering the insert ring also coversa portion of the heart valve.
 5. The sewing ring of claim 4, wherein thefabric covering both the insert ring and the portion of the heart valvealso connects the ring to the heart valve periphery at a seam, andwherein the sewing ring pivots between the first and second positionsabout the seam.
 6. The sewing ring of claim 1, wherein thesuture-permeable ring is attached to the heart valve periphery along aline, and wherein the sewing ring pivots between the first and secondpositions about the line.
 7. The sewing ring of claim 6, wherein thesewing ring comprises a suture-permeable insert ring and a fabric cover,and wherein the fabric covers the insert ring and connects the insertring to the heart valve periphery at a seam, the seam defining the lineabout which the sewing ring pivots.
 8. The sewing ring of claim 1,wherein the sewing ring includes a suture-permeable, generallyfrusto-conical insert ring and wherein the first and second positionscorrespond to the frusto-conical insert ring extending outward from theperiphery in opposite axial directions.
 9. The sewing ring of claim 8,wherein the insert ring includes alternating radially thick and thinregions facilitating pivoting of the sewing ring between the first andsecond positions.
 10. The sewing ring of claim 8, wherein the insertring has a radially undulating shape facilitating pivoting of the sewingring between the first and second positions.
 11. A prosthetic heartvalve having an inflow end and an outflow end, comprising: a generallyannular stent, and a suture-permeable sewing ring attached to aperiphery of the stent so as to be moveable between two positions,wherein in the first position the sewing ring extends generally towardthe outflow end of the valve and in the second position the sewing ringextends generally toward the inflow end of the valve, wherein first andsecond positions are stable such that the sewing ring is bi-stable. 12.The heart valve of claim 11, wherein the sewing ring comprises asuture-permeable insert ring and a fabric cover.
 13. The heart valve ofclaim 12, wherein the fabric covering the insert ring also covers aportion of the stent.
 14. The heart valve of claim 13, wherein a singlepiece of fabric is used to completely cover both the insert ring and thestent.
 15. The heart valve of claim 11, wherein the sewing ring attachesto the stent exclusively with a portion of fabric that also covers atleast a portion of the sewing ring.
 16. The heart valve of claim 15,wherein a seam is provided in the fabric defining a line of attachmentbetween the sewing ring and the stent, and wherein the sewing ringpivots about the seam between the first and second positions.
 17. Theheart valve of claim 11, wherein the suture-permeable sewing ring isattached to the stent periphery along a line, and wherein the sewingring pivots between the first and second positions about the line. 18.The heart valve of claim 17, wherein the sewing ring comprises asuture-permeable insert ring and a fabric cover, and wherein the fabriccovers the insert ring and connects the insert ring to the stentperiphery at a seam, the seam defining the line about which the sewingring pivots.
 19. The heart valve of claim 11, wherein the sewing ringincludes a suture-permeable, generally frusto-conical insert ring andwherein the first and second positions correspond to the frusto-conicalinsert ring extending toward the outflow end and the inflow end of thevalve, respectively.
 20. The heart valve of claim 19, wherein the insertring includes alternating radially thick and thin regions facilitatingmovement of the sewing ring between the first and second positions. 21.The heart valve of claim 19, wherein the insert ring has a radiallyundulating shape facilitating pivoting of the sewing ring between thefirst and second positions.